Early warning, marine style, with justification (5,4)
I believe the answer is:
alarm call
'early warning' is the definition.
(call to wake somebody up)
'marine style with justification' is the wordplay.
'marine style' becomes 'alarm' (I am not sure about this - if you are sure you should believe this answer much more).
'with' is a charade indicator (letters next to each other).
'justification' becomes 'call' (something unjustified is uncalled for).
'alarm'+'call'='ALARM CALL'
(Other definitions for alarm call that I've seen before include "Telephoned awakening" , "Robin, maybe, scared to give this" , "hotel service" .)